Ships, fishnets or other underwater structures or equipment tends to be attacked aquatic organisms such as barnacles, mussels, and algae, and the like. Organisms can grow and multiply and eventually cause significant problems. For example, in the case of a ship's hull, the growth of marine organisms on the hull can increase the frictional resistance between the hull and water, thus increasing fuel consumption and reducing the speed of the ship.
One approach to the problems is to coat the surfaces of the structures with an antifouling coating which contains a “self-polishing” polymer is present. “Self-polishing” polymers generally have hydrolysable groups within the polymer backbone. Over time, the polymer at the outmost layer of the coating is hydrolyzed and becomes water erodible residue. This water erodible residue is subsequently removed by water, resulting in a smooth, foul free surface. Such action is commonly referred to as a “self-polishing” effect, which continues until the antifouling coating is removed from the surface to which it is coated. At which time, a new antifouling coating must be placed on the surface. Generally, self-polishing polymers are typically acrylates with metal ester or silyl ester functionality.
Self-polishing polymers can be used in combination with biocides such as copper pyrithione to further enhance antifouling performance. Copper pyrithione utilized in the paints typically have relatively small particle sizes. Illustratively, EP 1 695 963 B1 discloses that if more than 20% of the copper pyrithione particles have a size of over 10 micron, then it is difficult to disperse the particles in a paint.
Unfortunately, in some formulations, copper pyrithione of a small particle size may leach out of the paint film too fast, particularly in warm water, thus compromising the antimicrobial efficacy of the paint.
Accordingly, there is a need in the paint manufacturing community to provide a paint that contains adequately dispersed copper pyrithione particles having larger particle sizes relative to conventional copper pyrithione particles utilized in the paint. The present invention provides an answer to that need.